1. Field of the Invention
This invention relates to a cold cathode and a cold cathode discharge device.
2. Description of the Related Art
A cold cathode discharge device represented by a cold cathode discharge lamp has a simple structure, which does not employ any heating filaments. Accordingly, because the device can easily be miniaturized and operate at a low temperature, and moreover has a relatively long life, it is widely put to use recently for a wide variety of lighting or a backlight of a liquid crystal display device.
On the other hand, because the cold cathode discharge lamp keeps discharging by means of secondary electron emission from the cold cathode due to ion bombardment of the discharge gas filled therein, it is usually required that a bias voltage should be applied near the cathode portion in order to generate a very high electric field compared with a thermal cathode used for a thermal cathode fluorescent lamp, etc. While the lamp is turned on, it is therefore necessary to supply a high voltage thereto, and consequently the cold cathode discharge lamp is inferior to the thermal cathode discharge lamp with regard to the conversion efficiency of electric power into light, because of the high electric field and the high voltage mentioned above. However the cold cathode type lasts longer than the thermal cathode type, so that it is frequently used for some applications where exchanging the lamp is not easy. In consequence, it is desired that durability of the lamp and a discharge device should be much more improved.